On the above diagram, draw the line that corresponds to the first ionization energy of hydrogen and explain your reasoning.

for showing the energy to remove electron from ${\text{n}} = 1$ to ${\text{n}} = \infty$ on the above diagram;

to ionize an element, electron must be removed from the atom/no longer under influence of nucleus/removed beyond ${\text{n}} = \infty$ / OWTTE;

Candidates in some schools, however, appeared not to have encountered these ideas at all. Common errors were to label the first energy level as${\text{n}} = 0$ rather than${\text{n}} = 1$ and to only include one transition for each series. Sometimes the arrows showing the transitions were shown from the bottom up.

While more candidates managed to obtain at least a mark with regard to the first ionization energy of hydrogen, it was less common to find the correct graphical representation of the first IE with diagrams which often were unrelated.